Rotary damper

ABSTRACT

The present invention provides a rotary damper capable of reducing the variation in size of a gap through which viscous liquid passes when the viscous liquid moves. from a pressure chamber to a non-pressure chamber, and capable of obtaining stable braking characteristics.  
     The rotary damper of the invention comprises a vane member  30  having an upper end surface  30   a , a lower end surface  30   b  and a tip end surface  30   c . The vane member  30  is disposed in a liquid chamber partitioned by the partition wall  10   d  in which viscous liquid is charged such that as the rotation shaft  20  rotates, the vane member  30  can rotates while allowing its upper end surface  30   a , lower end surface  30   b  and tip end surface  30   c  to respectively slide on a lower surface  60   b  of a closing member which closes an opening of the body case  10 , an inner surface of a bottom wall  10   e  of the body case  10  and an inner peripheral surface  10   c  of the body case  10 , the vane member  30  partitions the liquid chamber into a pressure chamber and a non-pressure chamber. The rotary damper further comprises a liquid passage  80  which has a large hole portion  81  and a small hole portion  82  smaller than the large hole portion  81 , which penetrates the vane member  30  in a direction substantially parallel to an axial direction, the large hole portion  81  being in communication with the pressure chamber, and the small hole portion  82  being in communication with the non-pressure chamber, and a valve body movably disposed in the large hole portion  81  of the liquid passage  80.

TECHNICAL FIELD

The present invention relates to a one-way rotary damper used fordelaying rotational motion when an open/close body such as lid or dooris opened or closed.

BACKGROUND ART

As shown in FIG. 7 for example, a conventional rotary damper of thiskind includes a rotation shaft 102 disposed along an axis of a body case101, partition walls 103 provided so as to partition spaces formedbetween the rotation shaft 102 and the body case 101, and a vane member104 disposed to be rotatable with rotation of the rotation shaft 102 ina liquid chamber partitioned by the partition wall 103 in which viscousliquid is charged. The rotary damper also includes valve members 105.Each the valve member 105 is substantially T-shaped as viewed fromabove, and has an engaging projection capable of engaging into a grooveformed in a tip end surface of the vane member 104 with a playtherebetween, and has an arc portion whose outer peripheral surfaceslides on an inner peripheral surface of the body case 101 as the vanemember 104 rotates.

Each the valve member 105 of the rotary damper includes is provided witha backflow groove (not shown). The backflow groove is closed when thevane member 104 rotates in one direction and viscous liquid passesthrough the backflow groove when the vane member 104 rotates in theopposite direction. An open/close body which is a subject to becontrolled rotates in one direction, e.g., in a closing direction, therotation shaft 102 connected to a shaft of the open/close body rotatesin association with the rotational motion of the open/close body, andwith this rotation, the vane member 104 rotates in the liquid chamber.Each the liquid chamber is partitioned by the vane member 104 and thevalve member 105 into two chambers, i.e., a pressure chamber 106 a and anon-pressure chamber 106 b. When the vane member 104 rotates, theviscous liquid in the pressure chamber 106 a is pressed and moved intothe non-pressure chamber 106 b. At that time, since the backflow grooveof the valve member 105 is closed, the viscous liquid moves through aslight gap formed between the outer peripheral surface of the arcportion of the valve member 105 and the inner peripheral surface of thebody case 101. This rotary damper exhibits a predetermined braking forceby a resistance generated when the viscous liquid moves, and can delaythe rotational motion of the open/close body.

On the other hand, when the open/close body which is the subject to becontrolled rotates in the opposite direction (opening direction), therotation shaft 102 rotates in a direction opposite from that describedabove in association with the rotational motion of the open/close body,and with this rotation, the vane member 104 rotates in the oppositedirection in the liquid chamber. With this, the viscous liquid in thenon-pressure chamber 106 b is pressed and moved into the pressurechamber 106 a. At that time, since the viscous liquid passes through thebackflow groove of the valve member 105 and moves, almost no resistanceis generated when the viscous liquid moves. Thus, the rotary damper doesnot exhibit the braking force and allows the open/close body to rotatewithout delay.

In the case of the one-way rotary damper capable of exhibiting thebraking force only when the rotation shaft rotates in one direction, thebraking characteristics are varied depending upon a size of the gapthrough which the viscous liquid passes when the viscous liquid movesfrom the pressure chamber to the non-pressure chamber.

In the above-described rotary damper, however, since the gap is formedbetween the inner peripheral surface of the body case 101 and the outerperipheral surface of the arc portion of the valve member 105 which canslide on the tip end of the vane member 104 in the circumferentialdirection, if a plurality of rotary dampers are manufactured, it isextremely difficult to make the sizes of all the gaps uniform.

That is, in order to make the sizes of the gaps uniform in theabove-described rotary damper, a precise working is required for atleast three parts, i.e., the vane member 104 which is integrally formedwith the rotation shaft 102, the valve member 105 and the body case 101.However, in the actual case, size precision of among the parts is variedand as a result, variation is generated in size of the gap formed byassembling these parts.

Thus, in the rotary damper having the above-described configuration, ifa plurality of rotary dampers are manufactured, the brakingcharacteristics are prone to be varied depending upon individual rotarydamper, and it is difficult to obtain stable braking characteristics.

Furthermore, when the vane member 104 and the rotation shaft 102 areintegrally formed together, in order to form a groove in the tip endsurface of the vane member 104 into which the valve member 105 canengage, the shape of a mold becomes complicated and the cost of the moldis increased and thus, it is difficult to reduce the manufacturing costof the rotary damper.

On the other hand, there exists a one-way rotary damper in which aliquid passage penetrating the vane member in its thickness direction isformed in the vane member, the liquid passage is provided with a valvebody which control the flow of the viscous liquid, a tip end surface ofthe vane member directly slides on the inner peripheral surface of thebody case and rotates. According to the rotary damper having thisconfiguration, even if a plurality of rotary dampers are manufactured,since the valve member is not interposed between the tip end surface ofthe vane member and the inner peripheral surface of the body case, it ispossible to reduce the variation in size of the gap (gap between the tipend surface of the vane member and the inner peripheral surface of thebody case) through which the viscous liquid passes when the viscousliquid moves from the pressure chamber to the non-pressure chamber.

However, in order to operate the valve body such that the liquid passageis closed when the vane member rotates in one direction and the liquidpassage is opened when the vane member rotates in the oppositedirection, it is necessary to provide a play in the liquid passage forallowing the valve body to move therein, and the thickness of the vanemember is adversely increased. Thus, if such a configuration isemployed, there is a problem that the rotation angle range of the vanemember is narrowed.

When the vane member rotates in one direction, in order to reliablyclose the liquid passage by the valve body from the initial time pointof the rotation, it is considered to provide a spring or the like forbiasing the valve body so that the valve body disposed in the liquidpassage having the play close the opening of the liquid passage on theside of the pressure chamber in a normal state. According to thisconfiguration, however, the thickness of the vane member is furtherincreased.

Since there is a limit for increasing the thickness of the vane member,a spring or the like is not conventionally disposed in the vane memberhaving a lateral liquid passage.

Therefore, at the initial time point of the rotation of the vane member,the braking force to be exhibited is prone to be unstable, and it isdifficult to reliably exhibit a braking force from that time point.

The present invention has been accomplished in view of the above points,and it is a first object of the invention to provide a rotary dampercapable of reducing the variation in size of a gap through which viscousliquid passes when the viscous liquid moves from a pressure chamber to anon-pressure chamber, and capable of obtaining stable brakingcharacteristics.

It is a second object of the invention to provide a rotary damper inwhich a valve body for controlling a flow of viscous liquid is disposedin a vane member, a thickness of the vane member can be reduced ascompared with the conventional technique, and when the vane memberrotates in one direction, the valve body can be operated such that aliquid passage is reliably closed from the initial time point of therotation.

DISCLOSURE OF THE INVENTION

To achieve the above objects, an invention described in claim 1 providesa rotary damper comprising

a rotation shaft disposed along an axis of a body case,

a partition wall provided so as to partition a space formed between therotation shaft and the body case,

a vane member disposed to be rotatable with rotation of the rotationshaft in a liquid chamber partitioned by the partition wall in whichviscous liquid is charged, wherein the vane member can rotates whileallowing its upper end surface, lower end surface and tip end surface torespectively slide on a lower surface of a closing member which closesan opening of the body case, an inner surface of a bottom wall of thebody case and an inner peripheral surface of the body case, the vanemember partitions the liquid chamber into a pressure chamber and anon-pressure chamber,

a liquid passage which has a large hole portion and a small hole portionsmaller than the large hole portion, which penetrates the vane member ina direction substantially parallel to an axial direction, the large holeportion being in communication with the pressure chamber, and the smallhole portion being in communication with the non-pressure chamber, and

a valve body movably disposed in the large hole portion of the liquidpassage.

According to an invention described in claim 2, in the rotary damper ofclaim 1, the large hole portion and small hole portion are substantiallycircular holes, the valve body is formed into a spherical shape having adiameter greater than an inner diameter of the small hole portion.

According to an invention described in claim 3, in the rotary damper ofclaim 1 or 2, the rotary damper further comprises a spring which biasesthe valve body such that the valve body closes a boundary portionbetween the large hole portion and the small hole portion of the liquidpassage in a normal state.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a rotary damper according to an embodimentof the present invention,

FIG. 2 is a sectional view taken along a line A-A in FIG. 1,

FIG. 3 is a sectional view taken along a line B-B in FIG. 2,

FIG. 4 is a sectional view taken along a line C-C in FIG. 3,

FIG. 5 is a sectional view showing a rotary damper according to anotherembodiment of the invention,

FIG. 6 is a sectional view showing a rotary damper according to anotherembodiment of the invention and

FIG. 7 is a sectional view showing a conventional rotary damper.

In the drawings, a reference number 10 represents a body case, areference number 10 d represents a partition wall, a reference number 11represents a pressure chamber, a reference number 12 represents anon-pressure chamber, a reference number 20 represents a rotation shaft,a reference number 30 represents a vane member, a reference number 40represents a valve body, a reference number 50 represents a lid member,a reference number 60 represents a guide member, a reference number 70represents a seal member, a reference number 80 represents a liquidpassage, a reference number 81 represents a large hole portion, areference number 82 represents a small hole portion and a referencenumber 90 represents a spring.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained in more detail based on anembodiment shown in the drawings below.

As shown in FIGS. 1 to 4, the rotary damper according to the embodimentof the invention comprises a body case 10, a rotation shaft 20, vanemembers 30, valve bodies 40, a lid member 50 and a guide member 60.

The body case 10 comprises a plate-like mounting portion 10 a having asubstantially rhombus shape as viewed from above, and a cylindricalportion 10 b having a substantially tubular type and a closed bottomsurface.

As shown in FIG. 3, the cylindrical portion 10 b has two partition walls10 d which are opposed to each other with the rotation shaft 20interposed therebetween. Each the partition wall 10 d projects in theaxial direction from an inner peripheral surface 10 c of the cylindricalportion 10 b, and partitions a space formed between the rotation shaft20 and the body case 10.

A tip end surface of the partition wall 10 d has a substantially arccross section and an outer peripheral surface of the rotation shaft 20slides on the tip end surface when the rotation shaft 20 rotates. Thetwo chambers formed in the cylindrical portion 10 b partitioned by eachthe partition wall 10 d are liquid chambers. Viscous liquid such assilicon oil is charged into each liquid chamber.

Each the liquid chamber is closed by a closing member comprising the lidmember 50 which closes an opening formed in an upper surface of the bodycase 10 and the guide member 60 disposed in the lid member 50.

Insertion holes 50 a and 60 a through which one end 20 a of the rotationshaft 20 is inserted through the lid member 50 and the guide member 60which constitute the closing member. A seal member 70 for preventingviscous liquid charged into each liquid chamber from leaking is disposedaround the guide member 60.

As shown in FIG. 2, the one end 20 a of the rotation shaft 20 projectsfrom the body case 10, the other end 20 b is fitted into a recess formedin an inner surface of a bottom wall (end wall which closes a bottomsurface of the cylindrical portion 10 b) 10 e of the body case 10, andthe rotation shaft 20 is disposed along the axis of the body case 10.

As shown in FIG. 2, each the vane member 30 is formed into a plate-likeshape having a predetermined thickness. A length between upper and lowerend surfaces 30 a and 30 b of the vane member 30 is substantially equalto a distance between a lower surface of the closing member (lowersurface of the guide member 60) 60 b and an inner surface of the bottomwall 10 e of the body case 10, and a diametrical length of the vanemember 30 (a length between the tip end surface 30 c and a phantom rearend surface of the vane member 30 which comes into contact with theouter peripheral surface of the rotation shaft 20) is substantiallyequal to a distance between the outer peripheral surface of the rotationshaft 20 and the inner peripheral surface of the body case 10 (innerperipheral surface of the cylindrical portion 10 b) . The vane members30 are opposed to each other with the rotation shaft 20 interposedtherebetween.

As shown in FIGS. 2 and 3, the vane members 30 are integrally formed onthe rotation shaft 20, and the vane members 30 are disposed such thatthey rotate as in the liquid chambers as the rotation shaft 20 rotates.By disposing the vane members 30 in this manner, each liquid chamber ispartitioned into two chambers, i.e., a pressure chamber 11 and anon-pressure chamber 12.

Each vane member 30 is formed with a liquid passage 80 which brings thepressure chamber 11 and the non-pressure chamber 12 into communicationwith each other. As shown in FIGS. 2 and 4, the liquid passage 80comprises a large hole portion 81 formed in a range of a thickness ofthe vane member 30, and a small hole portion 82 which is smaller thanthe large hole portion 81. The liquid passage 80 penetrates the vanemember 30 in a direction substantially in parallel to the axialdirection of the rotation shaft 20. The large hole portion 81 is incommunication with the pressure chamber 11, and the small hole portion82 is in communication with the non-pressure chamber 12.

The valve body 40 is disposed in the large hole portion 81 of the liquidpassage 80 such that the valve body 40 can move in the large holeportion 81. When the valve body 40 receives a pressure of the viscousliquid, the valve body 40 closes or opens a boundary portion between thelarge hole portion 81 and the small hole portion 82.

It is preferable that both the large hole portion 81 and small holeportion 82 are substantially circular holes, and that the valve body 40is a ball, preferably steel ball having a diameter in the above range,i.e., a diameter larger than an inner diameter of the small hole portion82 and smaller than an inner diameter of the large hole portion 81. Ifboth the large hole portion 81 and the small hole portion 82 aresubstantially circular holes and the valve body 40 is a ball, ahermetical state (sealing state) when the valve body 40 closes theboundary portion between the large hole portion 81 and the small holeportion 82 is excellent. As a result, it is possible to prevent thedeterioration of the braking force which may be caused by liquid leakagefrom between the valve body 40 and the boundary portion.

The rotary damper comprising the above members is used in a state inwhich the one end 20 a of the rotation shaft 20 is connected to theshaft body of the open/close body which is the subject to be controlled,and the body case 10 is fixed to the predetermined position. With therotational motion caused when the open/close body is opened or closed,the shaft body of the open/close body and the rotation shaft 20connected to the shaft body are rotated and with this rotation, the vanemember 20 rotates in the liquid chamber.

For example, when the rotation shaft 20 rotates in the braking forceexhibiting direction (in a direction shown with an arrow X in FIG. 3),the vane member 30 rotates and pushes the viscous liquid in the pressurechamber 11 while allowing the upper end surface 30 a, the lower endsurface 30 b and the tip end surface 30 c of the vane member 30 torespectively slide on a lower surface 60 b of the closing member whichcloses the opening of the body case 10, an inner surface of the bottomwall 10 e of the body case 10 and an inner peripheral surface 10 c ofthe body case 10.

The pushed viscous liquid flows into the large hole portion 81 of theliquid passage 80 formed in the vane member 30, but the valve body 40 ispushed against the boundary portion between the large hole portion 81and the small hole portion 82 by the pressure of the flowing viscousliquid, the boundary portion is closed by the valve body 40. Thus, theviscous liquid can not move into the non-pressure chamber 12 through theliquid passage, and moves into the non-pressure chamber 12 through theslight gap formed in the body case 10. That is, the viscous liquid movesfrom the pressure chamber 11 to the non-pressure chamber 12 through agap between an outer peripheral surface of the rotation shaft 20 and thetip end surface of the partition wall 10 d, a gap between the upper endsurface 30 a of the vane member 30 and the lower surface 60 b of theclosing member, a gap between the lower end surface 30 b of the vanemember 30 and the inner surface of the bottom wall 10 e of the body case10, and a gap between the tip end surface 30 c of the vane member 30 andthe inner peripheral surface 10 c of the body case 10.

The rotation speed of the rotation shaft 20 is reduced by a resistancegenerated when the viscous liquid moves through the slight gap. Withthis, a predetermined braking force is applied to the open/close body,and the rotational motion of the open/close body is delayed.

On the other hand, if the rotation shaft 20 rotates in a directionopposite from the braking force exhibiting direction (in a directionshown with an arrow Y in FIG. 3), the vane member 30 rotates in theopposite direction and pushes the viscous liquid in the non-pressurechamber 12 while allowing the upper end surface 30 a, the lower endsurface 30 b and the tip end surface 30 c of the vane member 30 torespectively slide on the lower surface 60 b of the closing member whichcloses the opening of the body case 10, the inner surface of the bottomwall 10 e of the body case 10 and the inner peripheral surface 10 c ofthe body case 10.

The pushed viscous liquid flows into the small hole portion 82 of theliquid passage 80 formed in the vane member 30, this pressure pushesback the valve body 40 which closes the boundary portion between thelarge hole portion 81 and the small hole portion 82, thereby opening theboundary portion. With this, the viscous liquid can pass through theliquid passage 80 and thus, the viscous liquid passes through the liquidpassage 80 and moves into the pressure chamber 11 swiftly and withoutgenerating a resistance almost at all. As a result, the rotation shaft20 rotates without being decelerated, no braking force is applied to theopen/close body and the open/close body rotates.

According to the rotary damper of this embodiment, when the rotationshaft 20 rotates in the braking force exhibiting direction, the liquidpassage 80 is closed and the viscous liquid moves from the pressurechamber 11 into the non-pressure chamber 12 only through the slight gapformed in the body case 10. Therefore, the braking characteristics arevaried depending upon the size of the gap through which the viscousliquid passes. According to the embodiment, the vane member 30 isdisposed in the liquid chamber such that the vane member 30 rotates asthe rotation shaft 20 rotates, while allowing the upper end surface 30a, the lower end surface 30 b and the tip end surface 30 c of the vanemember 30 to respectively slide on the lower surface 60 b of the closingmember which closes the opening of the body case 10, the inner surfaceof the bottom wall 10 e of the body case 10 and the inner peripheralsurface 10 c of the body case 10, and the vane member 30 rotates whilethe tip end surface 30 c slides on the inner peripheral surface 10 c ofthe body case 10. Thus, even if a plurality of rotary dampers aremanufactured, it is possible to reduce the variation in sizes of thegaps formed in the body cases 10 as compared with the conventionaltechnique, and stable braking characteristics can be obtained.

Since it is unnecessary to separately provide the vane member unlike theconventional technique, it is possible to reduce the number of parts andto reduce the manufacturing cost.

Further, the liquid passage 80 includes the large hole portion 81 formedin the thickness region of the vane member 30 and the small hole portion82 which is smaller than the large hole portion 81, the vane member 30penetrates the rotation shaft 20 in the direction substantially inparallel to the axial direction of the rotation shaft 20, i.e., in thevertical direction, the large hole portion 81 is in communication withthe pressure chamber 11 and the small hole portion 82 is incommunication with the non-pressure chamber 12, and the valve body 40can move in the large hole portion 81. Thus, the play allowing the valvebody 40 to move can be provided even increasing the thickness of thevane member 30. Thus, the thickness of the vane member 30 can be reducedas compared with the conventional technique.

Further, when the vane member 30 and the rotation shaft 20 areintegrally formed together, if the liquid passage 80 is formed in thevane member 30, the cost required for forming the mold can be reduced ascompared with the conventional technique in which the groove with whichthe valve member 105 can be engaged is formed in the tip end surface ofthe vane member 104. Therefore, the manufacturing cost of the rotarydamper can be reduced as compared with the conventional technique.

Further, both the large hole portion 81 and the small hole portion 82are substantially circular holes, and the valve body 40 is the ball.With this configuration, it is possible to enhance the sealingperformance, and to prevent a braking force to be exhibited from beingdeteriorated.

The liquid passage 80 penetrates the vane member 30 in the directionsubstantially parallel to the axial direction of the rotation shaft 20.Therefore, as shown in FIG. 5, a ratio of the liquid passage 80 occupiedby the large hole portion 81 is increased, and it is possible to providea spring 90 which biases the valve body 40 such that the valve body 40closes the boundary portion between the large hole portion 81 and thesmall hole portion 82 in a normal state.

The spring 90 is a compression spring. The valve body 40 is alwayspushed against the boundary portion between the large hole portion 81and the small hole portion 82 by the spring 90 to close the boundaryportion. Therefore, when the vane member 30 rotates as the rotationshaft 20 rotates in the braking force exhibiting direction, the liquidpassage 80 can reliably be closed by the valve body 40 from the initialtime point of the rotation. Therefore, the braking force can reliably beexhibited from the initial time point of the rotation of the vane member30, and rattle is eliminated.

When the rotation shaft 20 rotates in the direction opposite to thebraking force exhibiting direction and the vane member 30 rotatescorrespondingly, the valve body 40 is pushed back by the pressure of theviscous liquid, thereby compressing the spring 90 to open the liquidpassage 80.

Although the two vane members 30 are provided such as to be opposed toeach other with the rotation shaft 20 interposed therebetween in thisembodiment, the present invention is not limited to this configuration.The invention can also be applied to a rotary damper in which one vanemember 30 projects from the rotation shaft 20 as shown in FIG. 6.

INDUSTRIAL APPLICABILITY

As explained above, according to the rotary damper of the presentinvention described in claim 1, even if a plurality of rotary dampersare manufactured, it is possible to reduce the variation in size of thegap through which the viscous liquid passes when the viscous liquidmoves from the pressure chamber to the non-pressure chamber, and morestable braking characteristics can be obtained. The valve body whichcontrols the flow of the viscous liquid can be disposed in the rotarydamper without increasing the thickness of the vane member, and thethickness of the vane member can be reduced as compared with theconventional technique.

According to the rotary damper of the invention described in claim 2,hermetical state (sealing state) when the valve body closes the boundaryportion between the large hole portion and the small hole portion isexcellent. Therefore, it is possible to prevent the deterioration of thebraking force which may be caused by liquid leakage from between thevalve body and the boundary portion.

According to the rotary damper of the invention described in claim 3,when the vane member rotates in one direction, the valve body can beoperated such that the liquid passage is reliably closed from theinitial time point of the rotation, and it is possible to reliablyexhibit the braking force from that time point.

1. A rotary damper comprising a rotation shaft disposed along an axis ofa body case, a partition wall provided so as to partition a space formedbetween the rotation shaft and the body case, a vane member disposed tobe rotatable with rotation of the rotation shaft in a liquid chamberpartitioned by the partition wall in which viscous liquid is charged,wherein the vane member can rotates while allowing its upper endsurface, lower end surface and tip end surface to respectively slide ona lower surface of a closing member which closes an opening of the bodycase, an inner surface of a bottom wall of the body case and an innerperipheral surface of the body case, the vane member partitions theliquid chamber into a pressure chamber and a non-pressure chamber, aliquid passage which has a large hole portion and a small hole portionsmaller than the large hole portion, which penetrates the vane member ina direction substantially parallel to an axial direction, the large holeportion being in communication with the pressure chamber, and the smallhole portion being in communication with the non-pressure chamber, and avalve body movably disposed in the large hole portion of the liquidpassage.
 2. The rotary damper according to claim 1, wherein the largehole portion and small hole portion are substantially circular holes,the valve body is formed into a spherical shape having a diametergreater than an inner diameter of the small hole portion.
 3. The rotarydamper according to claim 1 or 2, further comprising a spring whichbiases the valve body such that the valve body closes a boundary portionbetween the large hole portion and the small hole portion of the liquidpassage in a normal state.